The present invention relates in general to light curtains which detect the intrusion of human limbs or other objects into a protective zone and, more particularly, the present invention relates to a system for mounting light curtains.
Light curtains are commonly employed in a variety of industrial applications to detect the intrusion of objects, such as hands or feet of personnel, into or around a prescribed area or zone of protection. Typical applications for light curtains include providing operator protection around machinery, such as punch presses, brakes, molding machines, automatic assembly equipment, coil winding machinery, robot operation, casting operations and the like. Light curtain systems employ invisible pulsed infrared light beams which project across a plane along the zone to be protected. Unintended blockage of the light beams by an object, such as the operator""s hand, is sensed such that a control circuit triggers a warning signal, shuts the machinery down or otherwise safeguards the area.
In order to function properly, transmitters and receivers of the light curtain must be properly aligned. In the past, alignment of the transmitters and receivers of the light curtain was very difficult. Transmitters and receivers of the light curtain must be properly positioned and oriented with respect to a horizontal axis, a vertical axis and depth axis. In the past brackets have been used to mount the components of the light curtain. Some prior art brackets are rigidly attached to the light curtain, making it difficult to properly orient the light curtain compartment about a vertical axis. Shims have been used to orient light curtain transmitters and receivers in a vertical axis.
U.S. Pat. No. 5,198,661 to Anderson illustrates mounting brackets that allow for rotative movement of the light curtain components with respect to the brackets. The mounting brackets of the ""661 patent are longitudinally fixed to ends of the light curtain component components.
What is needed is a light curtain mounting system that allows for rotational and longitudinal movement of light curtain components with respect to the mounting bracket. Such a system greatly eases alignment of the light curtain transmitters and receivers by allowing longitudinal and rotational adjustment of the light curtain with respect to the brackets.
The present disclosure concerns an apparatus for mounting optics of a light curtain that allows for longitudinal and rotational adjustment between a light curtain optics housing and a mounting bracket. The light curtain optics housing includes a curved mounting surface that extends along a length of the housing. The mounting bracket is connected to the curved mounting surface, such that the mounting bracket can be longitudinally adjusted with respect to the housing. The mounting bracket includes a curved inner surface and an adjustment slot through the curved inner surface that allows rotational adjustment of the housing with respect to the mounting bracket.
In embodiments of the invention, the curved mounting surface of the light curtain is defined by an outer surface of a pair of opposing mounting flanges that extend from the housing.
A threaded fastener that passes through the adjustment slot in the bracket is used to connect the mounting bracket to the curved mounting surface. The mounting flanges define a fastener retaining channel that allows for longitudinal adjustment of the bracket with respect to the housing. The housing is connected to the bracket by a fastener constrained in the fastener retaining channel and a second fastener that engages the curved outer surface of the mounting bracket. The center of the radius of the curvature of the curved mounting surface of the light curtain optics housing is located at a central axis of the optics mounting housing. A washer is used that has a curved surface and a flat surface. The fastener used to connect the housing to the bracket engages the flat surface of the washer to bring the curved surface of the washer into engagement with the curved outer surface of the bracket to bring the bracket into tight engagement with the housing.
In one embodiment, an internally threaded fastener is constrained within the channel defined between the pair of opposed flanges of the light curtain housing. The washer having a curved surface and a flat surface engages the curved outer surface of the mounting bracket. An externally threaded fastener engages the flat surface of the washer, extends through the washer and the slot in the mounting bracket and engages the internally threaded fastener to connect the bracket to the housing.
A method of mounting and aligning optics of a light curtain is performed using the disclosed apparatus. The curved mounting surface of the light curtain housing is loosely connected to the curved mounting surface of the mounting bracket. The curved mounting surface of the light curtain housing is rotated with respect to the curved mounting surface of the mounting bracket to an aligned position. The connection between the housing and the mounting bracket is tightened. These and other advantages of the present invention will become apparent upon reading the following detailed description in view of the drawings.